View Full Version : Displaying pictures on TV from SD card.
11-02-2010, 12:39 AM
I have been playing with the SD card read and write functions as well as some of the video apps by Rayman and Baggers. Has anyone setup a simple TV driver with a 'read picture from SD card and display it'? A BMP format would be ideal, but converting for the prop wouldnt be bad either. I have been using the TV and graphics objects to display the numbers 1 though 100 based on a voltage input and run out of ram real quick. It would be nice to use some more complex and nice looking numbers from bitmaps if they could be changed out at about 10fps without any visual glitches. Doable?
11-02-2010, 01:46 AM
The problem is that the Propeller's 32K of hub ram is not enough for a bitmap of any significant size, particular using anything other than a few shades of gray. The picture would have to be read from the SD card and converted to the actual bitmap on the fly ... not a difficult task, but you would see the "wipe" effect as one picture is replaced with another. Bill Henning does have a VGA driver for large bitmaps that uses his external memory. I think he was working on a TV driver using his external memory at one point, but I'm not sure. You'd have to check his mikronauts website.
You can't read from the SD card fast enough to produce the video "on the fly". You have to have a bitmap buffer for the whole screen.
11-02-2010, 02:53 AM
As Mike says, the limitation of using onboard RAM is 32K doesn't make a very big bitmap. This could be worked around by pre-processing the file to a tilemap+tile format. However, that doesn't get around the limited TV palette.
11-02-2010, 02:59 AM
I think I did post a bmp viewer for TV some time ago...
There is also a video player that Perry converted into a b&w video capture player/recorder recently...
11-02-2010, 03:49 AM
I picked up one of these WD media players recently for under $60, to play back WMV files (or still Jpegs could be done easily too).
It is compact (about 3" square) and comes with an IR remote control. I would love to be able to control it over the IR link from the prop
11-02-2010, 10:17 AM
Are you wanting bitmaps for the numbers? or are you wanting bitmaps in general?
What kind of size are you thinking?
Would you be ok with 128x96 fat pixels, but having 1 byte per pixel, giving you more colour range? or would 256x192 4 colours per 8x8 tile be ok?
When you want the image to change every 10fps, what size is that? or is it just the font image that would change?
11-02-2010, 02:36 PM
Here's the thread with the Windows BMP viewer for TV:
(I must admit that the new search engine makes this new forum software almost worth the switch)
11-02-2010, 09:11 PM
What I was looking for is an easier way to get nice graphics on a small screen via composite video. The pics below show what I have now and what I want. The first is the propeller at work, but i'd like to have more gauges and possibly allow for needle gauges and easy user configuration. Even with what you see and a VERY simple setup screen to set the trim, 32k is all gone. I was down to cutting every little thing from the tv and graphics objects just to make it fit and get rid of the screen artifacts when you over write the screen memory.
What I'm really looking for is the second picture which I dont think the prop can handle. I hate the idea of learning yet another language, but ive been messing with an FPGA and WOW what a learning curve. Short of blinking an LED I havent been able to get anything to work.
Propeller options? Other options?
11-02-2010, 09:28 PM
Have you tried using graphics.spin? That can sorta do what you want...
Never mind, I see that's what you're using...
Anyway, I'm working toward adding the Solomon SSD1926 chip to my 4.3" and 3.5" LCDs.
Then, I think you could do that. But, this is probably a couple months away...
11-03-2010, 02:40 PM
Ive been looking at other options like the 4dsystems chips and pic32's. Another option COULD be to user more than one propeller and 'stack' the images. I havent been able to find a chip yet that will stack more than one composite video signal into one. There are splitters and OSD chips, but nothing ive found to combine signals. Does anyone know of anything like this?
11-03-2010, 02:54 PM
Or you could go for something readymade?
The Picaso VGA/SVGA controller
The 'Graphic LCD Serial Backpack'
(limited to 160x128 or 128x64 resolution)